A significant problem with current surfactant containing formulations used in wash off application is the poor deposition of lipophilic actives materials onto the surfaces to be treated. Typical fabric care products such as laundry detergent compositions and fabric softener compositions contain 0.5% to 1% by weight fragrance.
U.S. Pat. No. 6,051,540 disclose that the amount of fragrance left as a residue on the clothes can be as low as 1% of the original amount of fragrance in the starting product.
Without being bound by theory, it is believed that the lipophilic (oil) active material in general and fragrance in particular is rapidly solubilised by the surfactant micelles in the so called micellisation process. As a result of this micellisation process only a few part of active material is depositing on the surfaces to be treated. Most of the lipophilic active material is washed off in the rinsing water; see for example the article by Yoshikazu Tokuoka et al. (Langmuir 1995, 11, 725-729) dealing with the solubilisation of some synthetic perfumes by anionic-nonionic mixed surfactant systems.
A classical method for enhancing fragrance deposition is admixing the fragrance with surfactants and especially with cationic surfactants contained in conditioner compositions. An alternative route involves the preparation of solid particles by admixing the fragrance with amphiphilic polymers for example as described in EP-A 0 469 228.
U.S. Pat. No. 4,152,272 and EP-A 0 346 034 show incorporation of perfume into wax particles.
U.S. Pat. No. 5,506,201 discloses a method for producing a fragrance-containing solid particle of improved substantivity for incorporation into laundry detergents which comprises of a fat component and a solid surface active agent like sorbitan ester.
U.S. Pat. No. 6,042,792 describes bioactive compositions for targeted delivery to skin, hair and fabric in solid solution in a wax or polymer matrix.
US2004/0256748 (Seok) describes a process for preparing silica microcapsules comprising the steps of dissolving tetraethyl orthosilicate (TEOS) into an aqueous solution containing a hydrolysis catalyst to control a degree of hydrolysis and contribute hydrophilicity or lipophilicity, adding a core material and an appropriate amount of aminopropyltrialkoxysilane (APS) as a gelling agent into the solution, and emulsifying and dispersing the resulting solution to a solution having a polarity opposite to that of the core material to microcapsulate by coating the core material with silica shell via a sol-gel reaction. In example 8 it is claimed that a liposoluble perfume is encapsulated.
FR2858637 describes a textile article containing microcapsules with shells in melamine or polydimethylsiloxane, the active product can be a perfume. The encapsulation is typically made by in situ polymerisation.
GB2416524 describes another in-situ polymerisation process where a lipophilic cosmetic, chemical, biological or pharmaceutical active material composition is encapsulated by mixing it with a water reactive silicon compound and emulsifying the mixture in an aqueous medium under shear and in the presence of at least one surfactant, thereby forming an aqueous suspension of microcapsules having a core of the active material composition surrounded by a shell of silicon-based network polymer. The polysiloxane shell is preferably made by condensation of a tetraalkoxy- or trialkoxy-alkylsilane such as tetraethoxysilane (TEOS). The preferred active material is a sunscreen.
WO2005/009604 describes a method for preparing microcapsules where an oily phase comprising a water insoluble precursor and the core material is emulsified in water. Then appropriate shear and temperature conditions are applied to form the microcapsules.
According to sol-gel or in-situ polymerisation processes described before, a precursor such as TEOS and an active ingredient are directly mixed together, emulsified in presence of a low amount of water then TEOS is polymerised in-situ. On the contrary, in a core-shell process, an aqueous emulsion of active ingredient is first made, then TEOS is added in the continuous aqueous phase under shear and an “ex-situ” polymerisation is conducted. As shown in the examples of the present description, microcapsules obtained by sol-gel or process tend to be of lower stability than core-shell microcapsules.